Actimel (DanActiva) is by court order not allowed to advertise with any health benefit in the UK.
http://news.bbc.co.uk/2/hi/uk_news/8305918.stm
since 2007, in the EU you are only allowed to advertise with health claims if you can scientifically proof the healthy benefits of your product. since the EU denies any claims that probiotics have any more health benefit than regular yoghurt:
http://news.bbc.co.uk/2/hi/health/8286646.stm
the claims by actimel and yakult mentioned in the article have been rejected or they took them back on their own to prevent further damage:
http://www.spiegel.de/wirtschaft/se...-danone-aendert-actimel-werbung-a-689263.html
today they only claim "can make you feel better" and ask people to test them - garnered with some confessions by celebs how good the prodcut helped them. classic placebo/snake oil. eat some regular yoghurt it helps you as much.
there are of course probiotics that work and even used to treat certain conditions. but again: probiotic yoghurts from the supermarket shelves are no better than any regular yoghurt.
there really isn't much to discuss about it. when multi-million-dollar companies cannot proof this (or fail in proving this), how the heck are you going to do it? if you could, you'd be really rich soon, since they would have big interest in that ..